"It's something we've never seen before," said institute president David Walsh, warning that today's games are "more extreme" and more easily available to underage kids than ever before.

In "Stubbs the Zombie," the lead character eats the brains of humans as blood splatters across the screen.

"It's just the worst kind of message to kids," said Sen. Joe Lieberman, D-Conn., who joined institute officials at a press conference announcing the group's 10th annual video game report card. "They can be dangerous to your children's health."

The institute showed video clips that included gang warfare against police in "The Warriors" and a rogue police officer gunning down victims in "True Crime: New York City."

"Blitz: The League" has scenes of football players hiring prostitutes and engaging in drug deals, Walsh noted. "Doom 3," "Resident Evil 4" and "Grand Theft Auto: Liberty City Stories" also made the list.

The institute's secret shopper survey found that 44 percent of child buyers were able to buy M-rated games with sexual and violent content intended for those aged 17 and over — an increase of 10 percent from a 2004 study.

Halpin pointed out that secret underage shoppers were turned down 56 percent of the time — nearly three times the number rejected in a 2000 study.

"This overall trend demonstrates strong and growing retailer commitment to video game rating enforcement, although clearly we are not yet where we want to be as an industry," said Halpin.

Walsh, meanwhile, cited increases of 3,000 percent in profanity and 800 percent in sexual content in M-rated games since the 1990s.

He also said the industry's Entertainment Software Ratings Board, which assigns game ratings, is "broken and beyond repair." Walsh's group plans to organize a summit next year to create a new ratings system.

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